The background description provided herein is solely for the purpose of generally presenting the context of the illustrative embodiments of the disclosure. Aspects of the background description are neither expressly nor impliedly admitted as prior art against the claimed subject matter.
Aircraft and vehicles, particularly those used in military and racing applications, are frequently subjected to strict weight requirements to maximize their capability to carry personnel, equipment and ordinance, as well as compete in the sport of racing. In some of these applications, for example, reducing the weight of a helicopter by just a few pounds may contribute to the carrying capacity of the helicopter. In such applications, therefore, it may be desirable to reduce the weight of as many components as possible of the aircraft, vehicle or other apparatus in order to reduce the weight of the apparatus to within or below the mandated weight restriction guidelines.
Reduction in weight of the components in vehicles which are subject to strict weight requirements may be necessary to optimize weight, strength and wear resistance of the components, particularly components such as gears which generate and transmit power. Due to its inherent strength and high melting point, titanium may be particularly applicable as the body or core of these components. However, titanium has low contact resistance and is vulnerable to immediate wear and galling. Thus, the use of a composite including titanium and some wear-resistant material such as steel alloys which modifies the surface of the titanium may be necessary to achieve this optimization.
Combining titanium and steel may theoretically be accomplished by soldering or brazing, mechanical fastening, thermal spraying, or by some form of cladding. However, due to component shape, differential thermal expansion, type of application loading or access to the attachment process, cladding is a viable option to facilitate application of the typically steel alloy wear-resistant material to the typically titanium core of the component.
In developing a lightweight composite material which is suitable for power transmission and heavy dynamic fluctuating stresses in the components, the juncture of the steel and titanium may undergo significant stress concentrations due to the differences in crystal lattice structures, microstructures, differential thermal expansion, and differential modulii of elasticity between these materials. Moreover, brittle intermetallics may be generated with the fusing of steel and titanium. Also, the typically steel contacting surfaces of these components will be exposed to another condition new to the industry. Gear teeth mesh, also known as gear contact ratio, is notoriously limited in gear applications. In such applications, it is difficult to ensure maximum surface area and evenly stress-distributed contact between gear teeth of meshing gears. By utilizing the less-rigid characteristics of titanium, it may be possible to a limited extent for mating gear teeth to better conform to each other through material deformation under load. Thus, this may require the steel surface of the gear teeth to deform and conform as well.
Accordingly, methods of fabricating reduced weight components while retaining contact wear resistance of the components, particularly power transmission components, for apparatuses which are subject to strict weight requirements by exploiting differences in the weights of materials used to fabricate the components may be desirable.